Vocus shares slumped to a 13-month low after the incident, before they recovered somewhat to finish the day 2.5% weaker at $5.49.
Horth, who ascended to the chief executive's post in February, has not made any public comment.
But Spenceley told The Australian: "Both Tony and I believed that a change was needed and we didn’t have a huge amount of faith in the CEO.
Vocus has grown to be a $3.5 billion telco through a number of acquisitions, one being a merger with the M2 Group in 2015.
Grist, who founded the WA-based Amcom, was behind the boardroom stoush. He sought a a change, claiming that there was a need for an executive shake-up.
He told The West Australian that the coup was in no way hamfisted, adding that his exit was merely a friendly one.
His intention was to bring Vocus' infrastructure side to the forefront as it had been sometime back, Grist said, adding that he wanted to re-engage Spenceley in the firm and concentrate again on the company's consumer Internet business.
The move to oust Horth was driven by his lack of an infrastructure background, he said. Horth was head of M2 Group, the owner of the Dodo and iPrimus brands, which Vocus took over in January.
Both Spenceley and Grist have sold down their respective stakes in Vocus before the stoush. Both are investing in new businesses.
Vocus is set to acquire Nextgen Networks, with the Australian Competition and Consumer Commission having approved the deal last month.